Vegetation Classification and Mapping Project Report - USGS

USGS-NPS Vegetation Mapping Program
Colonial National Historical Park
Vegetation Map Production
The final map for Colonial National Historical Park depicts 40 map classes. Twenty-six map
classes are crosswalked to USNVC vegetation associations, seven are nonstandard, park-specific
vegetation classes, and seven are Anderson land-use classes. Because of the difficulty of
distinguishing certain associations on aerial photography, two map classes, Tidal Oligohaline
Marsh and Tidal Mesohaline and Polyhaline Marsh, represent more than one USNVC
association. Polygons mapped as Tidal Mesohaline and Polyhaline Marsh represent vegetation
belonging to one or two associations. Polygons mapped as Tidal Oligohaline Marsh represent
one to five associations, occurring singly or as a complex. Polygons representing multiple
associations were not labeled to the association level. Each polygon representing a single
USNVC association was attributed with the appropriate USNVC formation and alliance based on
the hierarchy of the USNVC. Polygons mapped as nonstandard classes were also attributed to
USNVC formations when possible. The final map table includes 14 formations, 33 alliances,
and 24 associations.
The Kappa index for the final vegetation map exceeds the USGS-NPS VMP protocol
requirement of 80%. Errors of commission and omission reported for seven map classes fall
below the USGS-NPS VMP protocol requirement of 80%. Examination of the errors associated
with each observation shows they can be attributed to below minimum mapping unit inclusions
of other vegetation types within the target polygons, to the incomplete survey of target polygons,
to seasonal constraints in identifying certain associations in the field, or to observations made in
ecotonal areas transitional to other vegetation types. Additionally, some of the mapping errors
were due to the difficulty of distinguishing deciduous associations on aerial photography, since
many deciduous signatures are virtually identical.
Aerial photography flown in March 2002 served as the base map for the final vegetation map.
Since that time, the vegetation in the park has continued to change. In September 2003,
Hurricane Isabel altered the mapped vegetation in many areas of the park. The temporal
progression of transitional vegetation and the natural dynamics of coastal areas will continue to
alter the mapped vegetation, as will the park’s ongoing management of invasive species. Despite
these changes, the vegetation map produced by this project provides crucial baseline data for the
park resource managers.
Recommendations for Future Projects
Invasive nonnative plant species are the main threat to the native vegetation associations at
Colonial National Historical Park. Continued monitoring and management of invasive species in
and around all the natural communities in the park should be a priority for the park’s resource
managers. Early detection and control of invasive nonnative species on forest edges and along
trails and roads can help prevent new invasions. The most common and problematic species
include Japanese honeysuckle, Nepalese browntop, and common reed. Dormant season herbicide
application can be effective in treating Japanese honeysuckle infestations, but timing is critical. As
a rule, foliar application of 1.5% glyphosate (e.g., Roundup) after the first killing frost and before
the first hard frost is most effective (Nuzzo 1997). The annual, Nepalese browntop is a prolific
seed-producer, and seed banks can persist for at least five years (Tu 2000). Control of the
species can be very labor intensive (i.e., hand-pulling) or destructive to non-target plants (i.e.,
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